Delayed detonating means for projectiles



March 20, 1951 J. J. KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS FOR PROJECTILES e Sheets-Sheet 1 Filed Aug. 12,1943 INVENTORS .kr'ome JKZZ rlaizd March 20, 1951 J. J. KURLAND ETAL2,545,474

I DELAYED DETONATING MEANS FOR PROJECTILES 6 Sheets-Sheet 2 Filed Aug.12, 1943 INVENTORS I Jeram e .Zfiill ldlld BY Jos pk .ZKuI-Jand March20, 1951 J KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS FOR PROJECTILES Filed Aug. 12, 1943 6Sheets-Sheet 3 INVENTORS .ferome .Zfinrlazzd BY fisgplz .l jf urlandMarch 20, 1951 J. J. KURLAND ETAL 2,545,474

DELAYED DETONATING MEANS' FOR PROJECTILES Filed Aug. 12, 1943 6Sheets-Sheet 5 INVENTORS filom Harland BY .7059]: JKzzrJand March 20,1951 Filed Aug. 12, 1943 J. J. KURLAND EI'AL DELAYED DETONATING MEANSFOR PROJECTILES 6 Sheets-Sheet 6 4/ 4 fi/A 05 5 //44 /96 /42 47ban-5,4144 77m Scale Z/ Z/Z I f Z05 Z/O .Z/ Z06 Z/7 L I I I I I I I I II I I I Cal/braked 77me Scale 0 INVENTORS .ferome Jfiizrland Joe gr]:.1. I urland Patented Mar. 20, 1951 UNITED STATES OFFICE DELAYEDDETONATING MEANS FOR PROJECTILES Jerome J. Kurland and Joseph J.Kurland, Chicago, 111.

3 Claims.

Our invention relates to the detonation of ex plosive projectiles withcontrolled time delay and is directed to the use of what may be termed acondenser circuit for delayed action in fuses. Such a condenser circuitis charged at some initial potential distribution and is designed forprogressive change in that distributilon in such manner as to apply anefiective potential to suitable igniting means after a predeterminedtime interval.

One of the important problems in designing a time fuse incorporating acondenser circuit is to provide a thoroughly reliable and foolproofsafeguard against accidental or premature detonation. It is especiallydifficult to avoid serious hazard in th act of intially charging thefuse with the necessary potential.

Various safety expedients are known to the art. It has been suggested,for example, that a generator be built into the fuse for operation afterthe projectile is released, thereby to delay charging of the condensercircuit. Other suggestions have involved mechanical expedients for useduring the charging operation or special mechanical relationshipsbetween the fuse and the cooperating charging device.

One object of our invention is to meet this safety problem with completesuccess by simple structural means confined to the projectile and theassociated holding means for the projectile. An important advantage ofsuch an arrangement is that a simple and rudimentary charging device,free of complicated safety features, may be employed.

Many of the prior art suggestions may be used for projectiles ofrelatively large size which afford ample room for elaborate circuitarrangements and for moving parts, but such suggestions cannot inpractice he used for projectiles of relatively small caliber, 20 mm.shells, for example. A further object of our invention is to provide asafe and highly efiicient fuse construction'especially suitable forsmall caliber projectiles, a construction involving no moving partswhatsoever and lending itself to compact design. In this regard, afeature of our invention is the use of cerain safety shunts designed tobe opened automatically upon release of the projectile. Variouspractices of our inventions are based on various novel concepts of howsuch automatic action may be insured by simple expedients.

In a certain practice of our invention, we have the two-fold object,first, of employing a relatively low charging potential to achieve arelatively high ultimate potential and, second, of

avoiding hazard in the charging operation by employing an igniter thatis non-responsive to the initial relatively low potential applied by thecharging device.

In designing condenser circuits for the present purpose, it is notdifiicult to arrange for accurate delay periods within a narrow range oftime periods, especially within a range of relatively short timeperiods. It is difficult, however, to achieve suflicient accuracy overwide ranges and especially for relatively long time delays. One objectof certain practices of our invention is to achieve accuracy over wideranges of time values by novel arrangements involving the use of two ormore variable charging potentials. In one of these practices, it is ourpurpose to employ one or more auxiliary or modifying condensers for thedesired flexibility in time delay. In another teaching, we propose toachieve the desired accuracy and range by a novel form of chargingdevice in which the relative values of two charging potentials arevaried automatically for different time adjustments in a succession oftime ranges.

More specific objects and advantages of our invention will be apparentin the following description taken with the accompanying drawings.

In the drawings, which are to be considered as illustrative only:

Fig. 1 is a wiring diagram of one arrangement under our concept that maybe employed for the delayed detonation of explosive projectiles;

Fig. 2 shows the same diagram modified for elimination of moving partsand for adaptability to small caliber projectiles;

Fig. 3 is a diagrammatic view in cross section of an explosive shellincorporating the electrical arrangement of Fig. 2;

Fig. 4 is a wiring diagram of one of our arrangements involving the useof two safety shunts;

Fig. 5 is a diagrammatic view in cross section of an explosive shellincorporating the arrangement indicated in Fig. 4;

Fig. 6 is a wiring diagram of one of our electrical arrangementsinvolving the use of two different charging potentials with a safetyshunt;

Fig. 7 is a modification of the diagram of Fig. 6;

Fig. 8 is a diagrammatic view in cross section showing an explosiveshell incorporating the elec trical arrangement shown in Fig. 7;

Fig. 8a is a view similar to Fig. 8 showing a second structuralarrangement for incorporating the principles illustrated by Fig. 7;

Fig. 9 is a wiring diagram of another diiferentially charged circuitincorporating a safety shunt;

Fig. 10 is a diagrammatic view in cross section a u of an explosiveshell incorporating the electrical arrangements shown in Fig. 9;

Fig. 10a is a view similar to Fig. 10 of another structural arrangementbased on Fig. 9.

Fig. 11 is a wiring diagram indicating how one or more modifyingcondensers may be added to the basic circuit;

Fig. 12 is the wiring diagram of Fig. 11 modified to permit independentcharging of the additional condenser;

Fig. 13 is a wiring diagram illustrating our concept of initiallycharging a fuse nom'a low" potential source and subsequentlyautomatically increasing the potential after the projectile is released;

Figs. 14, 15, 16 and 17 are graphs explaining certain relationshipsinvolved in certain practices of our invention;

Fig. 18 is a diagram indicating the construction of an adjustablecharging "device based on relationships shown in Figs. 16 and 17.

Fig. 19 is a graph indicating relationships involved' in a second'formof adjustable charging device; and

Fig; 20 is a diagram indicating the construction of this second form ofadjustable charging device.

It is to be understood that our invention is widely" applicable to:projectiles, the invention having'utility not only forexplosive shellsdis-' charged from guns, but also for such explosive projectiles asaerial bombs, mines of various types, torpedoes andgrenades. The termprojectile as used hereinafter covers any of such explosive devices orthe like.

In'many practices-of our invention aholding means for a projectile has aspecial cooperativerelationship with the timing circuits employed fordelayeddetonation. The term"holding means may refer to various devicesin various practices of our invention and is therefore to be broadlyconstrued; For example, ifthe projectile is shot from a gun, either theshell case or the gun, or both,- may be regarded as the holding means.

If the projectile is an" aerial bomb; the holding means may be a bombrack or any part of aircraft from which the" bomb is released. It willbe apparent that the invention is applicable even to hand grenadessincethe'throwers hand or some device-retained in the throwers hand may bethe holding means under our concept.

In thesimple'form of our invention illustrated byFig: 1, tank: condenseror ignition condenser 20 is in series with what may be termed a timingcondenser'2 l, the two condensers being mutually opposed andbeingconnected to a'common ground 22. Interconnecting the potential orchargereceiving terminals of the twocondensers are an igniter 23 andacurrent-blocking means 25 arranged in series. The timing condenser 2|is shunted by a suitable resistance 26 serving a a current-leakage meansand may also be shunted by" a wire 2'! controlled by an impact switch28. For the purpose of charging the condenser circuit, a chargingcontact 39 is connected to the potential side'of the-condenser 29 by awire 3! and is connected to the potential side of the condenser 2| by awire 32, there being a normally closed safety switch 33 controlling"current flow through the wir 32. The safety switch 33 is designed toopen automatically'whenever' the projectile is released; In a shell, forexample, wemay use an inertia switchthat snapsopen in response toacceleration This actuation of of the shell in the gun barrel. a safetyprotective device, which, prior to'such actuation, will'normally preventany current from 4 flowing through the igniter, is referred to as armingof the projectile.

In preparation for release of the projectile, a suitable charging meansis applied to the described circuit. In the practice of the inventionexemplified by Fig. 1, it is contemplated that the charging means willbe in continuous communication with the condenser circuit up to themoment the projectile is released. In Fig. l the charging means is shownas including a charging contact 35 connected to a grounded battery 3?.If the delayed action fuse is not grounded through the holding means forthe projectile, the charging means may also include a grounding contactfor the fuse circuit. 7 7

As soon as communication between the charging device and th'econdensercircuit is broken by release of the projectile, current leakage throughthe resistance 26 causes the charge on thetiming'cond'enser' 25 todecrease with a corresponding drop in'potential across the timingvcondenser, the charge'on the tank condenser 2i}- meanwhile remainingconstant in the absence of i any closed conducting path. As the voltageacross the timing condenser decreases, an in-' creasing potential dropis established across the current-blocking means 25. When this potentialdifference across the currentblocking means reaches a predeterminedvalue, a conducting path is established to permit flow of current fromthe tank condenser 20 to a lower potential level, such current flowcausing the igniter 23 to be energized for detonation of the projectile.

The igniter 23' may be a conventional heat-" ing cap or detcnating.primer, or may be" a'suitable filament such as employed in flash bulbs.The current-blocking means'EE'may be' a gap means such as a gaseoustube'in which the gas closely related in function and may therefore bejointly covered by the term igniter or the term igniting means; in fact,the function of blocking current'and the function ofig'nition proper mayconceivably be combined in one element by using an explosive dielectricto bridge'a-gap in the circuit. 7

Fig. 2 is identicalin most respects to Fig. 1, as indicated by the useof corresponding numerals to designate corresponding parts. In thissecond circuit, however, there is no switch along the wire 33 sinceit-is contemplatedthat some provision will be made for automaticallybreaking the wire 33 when the projectile is released. The wire 33 may bebroken'at any point, for example, at the dotted line 'yy, or both thewire 33 and the wire 35 may be broken as indicated by the dotted line.rx. The arrangement is especially suitable for projectiles ofrelatively small caliber as illustrated by Fig. 3.

Fig. 3 shows'a projectile-or shell w'mounted in a case 4!, theprojectile containing suitable explosive material and a fuse body 52.The nose of the projectile may'be'provid-ed with an im'- pact plungerfl3 to close the previously mentioned impact switch 28. The chargingcontact 3B for the fuse circuit'may be of any suitable construction andmay be placed at any suitable location. Fig. 3, by way'of example, showsthe-charging contact 30 in the form of a concentric metal ring in thebase of the case 4|, the ring being suitably insulated from the metalmaterial of the base. The previously mentioned wires 3! and 33 extendfrom the fuse body 42 through suitable apertures in the base of theshell 40 and are terminally connected to the annular charging contact30, preferably at spaced points thereof as indicated.

To arm the shell shown in Fig. 3 for delayed detonation, a suitablecharging means incorporated in the associated gun construction isautomatically brought into communication with the annular chargingcontact 30, as indicated diagrammatically in "Fig: 3. projectile it isreleased following detonation of the primer id in the base of the case4|, the movement of the projectile away from the case causes the twowires 3! and 33 to be broken thereby destroying the safety shunt andmaking the condenser circuit operative for delayed ignition of theprojectile charge.

In the circuit shown in Fig. 4 a tank condenser 45 is connected to acharging contact 46 by a wire 4'1 and a timing condenser t8 shunted by ableeder resistance 50 is connected to the same charging contact by awire 5|. Current through the wire H is controlled by a normally closedsafety switch 52. The potential sides of the two condensers A5 and t8are also interconnected in series by a gaseous tube 53 or equivalentcurrent-blocking means. The other sides of the two condensers t5 and 48are connected to ground by wires 55 and 56 respectively, current throughthe wire 56 being controlled by a normally closed safety switch 51. Theground sides of the two condensers are interconnected in series by anigniter 58. For instantaneous firing, a wire 60 may connect thepotential side of the condenser 45 with the ground side of the condenser48, current flow through the wire being controlled by a normally openswitch 6| designed to close when the projectile strikes an object.

If the circuit shown in Fig. 4 is employed in a projectile of largecaliber, the two safety switches 52 and 51 may be inertia switches of awell known type designed to open when the projectile is initialyaccelerated. Prior to the opening of the two switches, no operativepotential difference can be established across the gaseous tube 53 andno eifective current can flow through the igniter 58. Prior to releaseof the projectile, a; complementary charging means in communication withthe charging contact 46 maintains both of the condensers at the samepotential with small current flow continuously through resistance 50 toground. When the projectile is released thereby breaking communicationwith the complementary charging means and causing the two switches 52and 5? to open, the circuit operates in the previously described mannerto build up a potential across the gaseous tube 53 and ultimately causedetonation through the igniter 58.

In View of previous discussion, it will be readily apparent that thecircuit shown in Fig. 4 may be adapted for small caliber projectiles byomitting the two switches and providing for breaking the shunt wires.Instead of arranging for wires to be broken to open the safety shunts,we may design the projectile for mechanical opening of the shuntsincidental to release of the projectile from the holding means.

In Fig. 5, in which we illustrate this latter concept, we show a smallcaliber shell 62 mounted As soon as the 6 in a casing 63, there being afuse body 55 inside the shell. At the end of the shell is shown animpact plunger 66 for actuating the previously mentioned impact switch6!. Fig. 5 also shows how we may arrange the wires 41, El, 55 and 55 ofthe wiring diagram in Fig. 4. Wires 55, and 56 terminate in two contacts61 and 63 respectively, these contacts being insulated from the materialof the shell 62 but being positioned to touch the metal of the case 63thereby to provide ground connections. Wires 4! and 5| terminaterespectively in two contacts H1 and ll in a socket 12 formed in thebottom of the shell 62. Mounted in the case 63 is a rigid conductor 13designed to enter the socket I2 and provide 'a conducting path from thetwo contacts iii and H to the previously mentioned charging contact 45.In this particular construction, the charging contact 46 is in the formof a metal ring mounted in the base of the case 53 with suitableinsulation. Fig. 5 shows how the previously described charging means,including the contact 35 and the battery 3? may touch the chargingcontact 46 when the projectile is placed in a gun.

There are certain inherent limitations in circuits in which a singlecharging contact is employed for charging both the tank condenser andthe timing condenser in the manner described above. Since the chargingvoltages applied to the two condensers are necessarily equal, timeadjustment can be achieved only by varying the common charging voltage.This fact may be readily understood by referring to Fig. 14 in which thecurve represents voltage decay across the timing condenser and orrepresents the striking voltage of the gaseous tube or othercurrentblocking means incorporated in the circuit. One limitation isthat zero time delay can be obtained only by using an infinite initialcharging voltage. Another limitation is that the charging voltage mustbe lowered to increase the time interval so that a relatively long delayperiod will require that the circuit be operated at a relatively lowenergy level.

These limitations can be eliminated by charging the two condensersdiiferentially. For convenience, an arrangement wherein the condensersare charged equally may be referred to as a simplex circuit and anarrangement providing for differential charging may be referred to as aduplex circuit.

The advantages of a duplex circuit may be understood by referring to 15,in which E2 represents an unvarying voltage applied to the tankcondenser in our circuit and the curve of voltage decay represents arange of potentials through which the timing condenser may be initiallycharged. It is apparent that zero time delay may be obtained simply bycharging the time condenser initially with a voltage less than E2 by theamount 'Ut. For a relatively short delay period the initial charge onthe timing condenser would be less than E2 by an amount slightly lessthan Ut. For relatively long delay periods the initial charge on thetiming condenser would be higher than the voltage E2. It is clear that aduplex circuit provides a greater range of time adjustment than asimplex circuit without the necessity of dropping to an undesirably lowenergy level.

Fig. 6 shows a duplex circuit in which a charging contact 15 isconnected to the potential side of a tank condenser 16 by a wire T1 anda second charging contact 18 is connected to the potential side of atimingcondenser- 811" by awire' 81, the timing condenser being shuntedby a bleederresistancemii. A wire 83'interconnects a gaseous tube 34 andan igniter 85, the tube and igniter interconnecting the potential sidesof the two condensers in series. Both of the condensers are grounded asshown. For percussion detonation, an impact switch 86 may controla wire8'! that extends from the above mentioned wire83' to ground. Our safetyshunt for this circuit isushown as a wire 88 from wire 83 to thecharging contact 15, current through this shunt wire being controlledbya normally closed safety switch 90.

The mannerin which the circuit sho-wn'in Fig. 6 functions may be readilyunderstood from our previous discussion. For relatively short timedelays; the voltage E1. applied to the charging contact 78 is relativelylow, this voltage being increased for longer delay periods. If theCir-"- cuitis employed in a large caliber projectila the safety switch9%! may be operated by inertia as heretofore suggested.

As heretofore stated, the igniter maybeoonsidered as the igniter 35proper or the igniter 85 in combination with the gaseous tube 84.'Accordingly, our safety shunt may straddle the igniter 8-5 alone asshown in 6 orm'ay by-pass both the igniter '85 and the gaseous tube 84as shown in Fig. '7;

Fig. '7 is largely similar to Fig. 6 as indicated bythe use ofcorresponding numerals for corre' sponding parts. It will be noted thatthe safety shuntwire 89 in Fig. '7 is'connected with theterminalof thegaseous tubexB'd on the side towards the timing condenser 8E} and that aresistance 95 is introduced between the gaseoustube and. the timingcondenser.

The advantage of the arrangement in Fig. '7" over the arrangement inFig. 6 is that the potential E2 is applied-to both sideso'f the gaseoustube and therefore cannot cause the tube'to strike in course ofthe"charging procedure. The resistance 94 is introduced because'thed'ifierence in potential between E1 and E2 necessarily exists betweenthe gaseous tube and thetiming condenser.

Either the circuit of Fig. 6 or the circuit of Fig. 7 may beincorporated in asmallcaliber projectile, the shunt switches beingomitted and means being provided to break the shunt wires. Fig. 8, forexample, shows how the circuit of Fig. 6 may be used in a small calibershell.

Fig. 8 shows the usual shell 9i mounted in. a case 92. inside the shell95 is a fuse body 93 and the above mentioned impact switch 86 positionedfor actuation by an impact plunger 95. The charging contacts '55 and 18of Fig. 7 may be mounted anywhere on the holding means or case 92. Byway of example, Fig. 8 shows the two contacts 55 and is in the form ofsuitably insulated metal rings exposed on the periphery of the case 62.A wire at is shown connected to. the metal shell of the projectile Stfor the purpose of grounding the two condensers l6 and 80. Also shownin. Fig. 3 are wires i7, 8! and 88 of the. diagram in Fig. 7, wire 8ibeing connected to the ring-shaped contact l8 and wires Ti and 88 beingconnected to the other ring-shaped contact 15.

When the projectile shown in Fig.3. is'placed in a gun, a suitablecharging means is automatically brought into electrical communicationwith the two ring-shaped contacts. T-andl8 asindicated diagrammaticallyin Fig. 8. When. the

pfoiiectile' is feleas'edby detonation -o e: material in'the ca'segztliethreewir's-fi, 8i rid se r'e 'automaueany broken. The f'rhanfier-inwhich the cirouitfurictions thereafter foddelayed deto'nation' is"apparent. I

*While Fig. 8 shows the twocnar'ging contacts 15-" and! 8 mounted on thecase '92-, these charging-contacts maybe mounte'don the'projctile 9|.Fig. 8a indicates how the arrangement ih 8 rnay be modified to shift'thecontacts from the'casef-to'theshell. Note that the case 9 in thisfi'gure' is of conventional-constructionthere being no necessity formodifying the case many manner. 7 g p The projectile 98 in Fig. 8 a isprovided with twodnsulatedi exterior rings toserv'e as contacts T5'andl8respectiv'ely. The'ground wire 96 from the fusebody 831s conn'cted asbefore to'the rh'aiter-iaro'f theprojeo'tile. Wire BI is connected tot-he npper ring '53 and wires 'lTand BBarebOhnected to the: lower ringv75.

A feature of the arangement shown in Fig. 8a is the'concept-of makingthewire 83 relatively longwso that the wire may be passed throughsuitableapertures in thebottom of the'projectil'e to-form-a loop mil inthe interior of the case 97. The purpose of providing such a loop is tomake thes'afety shunt wire 88 vulnerable to the ex"- plosion thatpropels the projectile. It is con templated that the explosion willde'stroya't least a portion of the wire formingthe loop H10 therebyopening the safety shunt; Whiienoiurther p'ro vision for' brea-king theshunt isnecessariy; some means may be provided onthecase Q'i to engagetheloop insure mechanical severance of the Wire as the projectile-leavesthe:'case. For example, a pin or hook It! may be-mounted on theinterior of the case 9"! to extend through th e loop [00.

Fig. 9; illustrating anotherarrangemen tof our duplexcircuit, shows;acharging contact I02 connected by awire N33 to the 'potential'sideof atank condenser r and-"shows achargingv con tact: H18 connected tothepotential :side'of atimingcondenser it? by a wire M8; the timingcondenser being shunted-by the usual bleeder resistance it. Thepotentialsides-of the two condensers are-connected in series with agaseous tube: I] I and the ground sides of the two condensers. areinterconnected in series by an igniter iii In this particular circuitour safety shunt is on the ground side ofthecondenser-s: By wayofe'xampl'e, weshow a wire i lt for grounding the tank condenser lileand a second 'wire H Sgrounding. the. timing condenser IU-l. A safetyswitch- We is. shown forbreaking currentthrough the wire H5 butobviously such a switch may be employed to control current throughwire'l l3 instead. Forihstahtaneous detonation; we show a shunt acrossthe condenser Hi1 controlled by an impact switch- H7.

It the circuitof'Fig. 9 is employed: in alargecaliber projectile, thesafety switch may be 013-- elatedby inertia or in any other automaticman ner. On the other hand, if it is desirable to omitthe safety switch,provision may be made to break either or both of the two wires-l l3 andl l5.

The provision for breaking the wire or wires ofthe safety shunt on theground side in Fig.9 may be in accord with any of the teachingsexemplified by Figs. 3; 5, 8'ancl' 8a.. Thus, in Fig; 10 we show anarrangement inwhich both wires 3i and H5" are isolatedmechanically whenthe projectile is released. I m

Fig. 10 showsa projectile H8 mounted in a case H9 in the usual manner.

The projectile contains the usual fuse body I23, above which is shown animpact plunger I2I for closing the previously mentioned impact switch'1. The two grounding wires H3 and H5 terminate respectively in twoinsulated contacts I22 and I23 positioned on the periphery of theprojectile II8 to touch the metal surface of the case H9. As heretoforesuggested, the charging contacts I52 and I96 of the circuit in Fig. 9may be placed anywhere on the case H9. In the present construction, thetwo charging contacts I62 and I06 comprise two insulated concentricmetal rings in the base of the case I I9, one ring being connected towire I63 and the other ring being connected to wire Hi8.

The manner in which the arrangement in Fig. 10 functions may be readilyunderstood. When the proiectile H3 leaves the case N9, the two wires I83and. WE are automatically broken, and

the ground connections shunting the igniter are opened by movement ofthe contacts I22 and I23 away from the case.

The purpose of Fig. 100: is to indicate how the arrangement in Fig. 10may be modified to place both of the charging contacts on theprojectile. The two charging contacts I02 and IE6 are in the form ofinsulated rings, wire I03 being connected to the ring I 02 and the wireI 68 being connected to the ring I06. Since the two rings I52 and I36are insulated from each other, it is not necessary to break the wiresI03 and I55. Both of the wires H3 and H5 are connected to the metalmaterial of the projectile for grounding but at least one of the twowires is arranged for automatic severance. Thus Fig. 10a shows the wireH5 connected terminally to the projectile but passed through suitable aerture through the projectile to form a loop I25 in the interior of thecase. As heretofore suggested, a pin or 'hook I26 may extend from thecase through the loop I25 but it is not necessary.

The purpose of Fig. 11 is to exemplify our concept of incorporating in aduplex circuit one or more modifying condensers to affect the rate atwhich potential drops across the timing condenser thereby to vary theperiod of time delay. Those skilled in the art will rea ily understandthat the addition of such modifying means affords additional flexibilityin the operation of the circuit.

In Fig. 11, a charging contact I2! is connected by a wire I 2-8 to thepotential side of the tank condenser I3!) and a second charging contacti3I is connected by a wire I32 to the potential side of a timingcondenser I33, the timing condenser being shunted. by the usual bleererresistance I35. A suitable gaseous tube I 35 is shown in series with thepotential sides of the two condensers while an igniter I3! is shown inseries with the ground sides of the condensers. Wires I45 and HH groundthe tank and timing condensers respecively. The circuit as described tothis point will be recognized as corresponding to Fig. 9.

We show only one auxiliary or modifying condenser I 42 in Fig. 11 but itwill be understood that any number of such additional condensers may beemployed. A wire I43 connects the potential side of the timing condenseri333 with the potential side of the modifying condenser I 42 and asuitable bleeder resistance I45 condenser connects the ground side ofthe modifying condenser with the ground side of the timing condenser.The ground side of the modifying condenser I42 is connected to groundthrough a wire I46.

It is apparent that the modifying condenser I42 will be initiallycharged with the same potential E1 as the timing condenser I33 and thatthe modifying condenser, like the timing condenser, will have its chargeopposed to the charge on the tank condenser I30. If this circuit isincorporated in a projectile, some means is provided for cutting off thethree condensers from each other, for example, by severance of the threewires I 40, I M, and I 45 along the line :r-.r by any of the variousexpedients heretofore suggested.

When the projectile having the circuit in Fig. 11 is released, therebyisolating the charging contacts I21 and I3I from each other and therebybreaking the three ground wires, current fiows through the resistance Ito lower the potential difference across the timing condenser I33. Therate at which this potential difierence decreases, however, is modifiedby current flow through the bleeder resistance I from the modifyingcondenser I42. Ultimately the voltage opposing the charge on the tankcondenser I30 decreases until detonation occurs.

Fig. 12 shows a variation of Fig. 11 corresponding parts being indicatedby corresponding numerals. Fig. '12 differs from Fig. 11 in providingfor independently charging a modifying condenser I4'I so that threedifferent potentials may be employed for adjustably varying the periodof time delay. In addition to the charging contacts I21 and I3Ipreviously mentioned, the circu t includes a third charging contact I48that is connected by a wire I50 to the potential side of the modifyingcondenser MI. The potential sides of the timing condenser I33 and themodifying condenser I 41 are interconnected by a bleeder resistance I 5|and the ground sides of the two condensers are interconnected by a wireI52. The manner in which the circuit functions may be understood withoutfurther explanation.

Fig. 13 illustrates our concept of how a relatively low chargingpotential may be employed in the field to provide a relatively highigniting potential after a projectile is released, the increase inpotential being accomplished by shifting a plurality of condensers fromparallel relation to series relation. Fig. 13 shows a plurality ofignition or tank condensers, there being, for example, three suchcondensers I53, I54 and I55. The potential side of the tank condenserI53 is connected by a wire I51 to a charging contact I58 and isconnected by a wire I60 to one side of an igniter I6I. The tankcondenser I54 is connected on its potential side to a charging contactI62 and a switch contact I63. In like manner, the tank condenser I 55 isconnected on its potential side to a charging contact I65 and a switchcontact I66.

The ground side of tank condenser I53 is connected to a switch memberI61 that normally rests against a grounded contact I68 but is adapted toswing automatically against the switch contact I63 when the projectileis released from its holding means. In like manner, the ground side ofthe condenser I54 is connected to a switch member III that initiallyrests against a grounded contact III but subsequently swingsautomatically against switch contact I66. The third tank condenser I55is permanently grounded. It is apparent that the arrangement providesfor initial parallel charging circuits through the three tank condensersI53, I54 and I55.

To complete the final ignition circuit, the second side of the igniterI6I is connected by a Jilil -wire- H3 to-asuitable gaseous tube: I15and-:the gaseous .tube is-connected linrturn by :a :wire: H6 1 to: thepotential side of a: timing condenser Ill. .The timing condenserl'l'|,*which is: shunted-by the,,usua1 timing-resistance 1-80, isconnected on .its,;potential siderto a charging contact WI: andconnected to-ground one the otherside by -.a wire !82. Asafety switch-I83"may be employed connected so as to shunt the igniter 16!.

Fig. -'13 showsvdiagrammatically -a charging meansin which four:contacts corresponding to the (four charging-contacts 158,162,. [GS-and18! of the circuit are all'energ-izedat-thesamepotentialby a commonbattery H2, the battery. affording a relativelyilow potential.

"of: our invention, however, the vario-uscondensers maybechargedatidifierent potentials.

'Whenthe projectile-is.released from. its. holding-:means, thefour-chargingcontacts become isolated fromr-each other :and. the twoswitches ltliand H are operated by-inertiapr othenauto- "ma-tic iactiontoa-shift the; plurality ,-of tank condensers from parallelrelation-to=series relation -therebytadding. :thecharges .to. produce-.-a relatively high potential across :ithecci-rcuit. opposed byuthecha-rgeonazthetim-ing condenser Ill. As .has previously ,been described, they"release. .of .the -,projecti-1e.wi-1l o erateto'open the normallyclosedsafety switc.h;l8,3,. onto-sever the igniter shunt ..wires along theline vs-+43, T thereby-serving to iarm the projectile. .The opposing-potent ial across the timing condenser ,progressively l-dewcreasesbecause of: current flow through. the resistance i803 andeventually the. high potential across the tank, condenser :becomeseffective-to I lump-a across the gaseous tube l and, detonate .theigniter l BI.

,Fol'racclllafly instime measurement .by our du- -..plex circuitthe-slope of-a curve of voltage values plotted {with respect totimeshould .be such-that -given voltage .di-fierences representcommensurate differences :inatime periods. Ifltheucur-ve -is too steep,a; given change. in potential represents .an .undesirablysrnall.change-,in time; :on the. other ..hand, .the same change; -in .potentialalong .a

flattened. curve 1 represents ..an excessively glarge change, in time.

We have found-that for accurate. time-control different relationships:between- E 1, the timingcondenser charge, and -;"E2, the tank;condenser .Chalge, .must :be employed in difierent time -ranges. .Thusifor-accuracyin.- an.-.initial, range .of relatively. short time periods,E2 must'be relativelyhigh, whereas over-.aa range of relatively longtimeperiods :52 must be relatively low. We ..have: 'further.discof/eredtthatv these tWot.-extr.eme ranges of time changes. may becorrelated in such manner as to afford a smooth andgraduali-proig-ression of [time values. Gnesmanner- -of ...corre--lating the two extreme. ranges 10f time; changes .is by introducingramid. range.

The graph in-Fig. lfirshows an initial range V of relatively-smalltimepriods in whichrEz is relatively; high. Itr-is assumedpbyway'ofillus-- tration, that-in a.- .particular duplexcircuit the strikingvoltage 115 of the gaseous tube-is 400 volts and that E2. throughout theinitial range is maintained atHQOO volts, E2 noinus we equalling 500volts. .ln the: midrange-of time-values E2 substantially equals E1,both. diminishing progresrsivelyas indicated. Since, Ezis'constant overthe initial= range and since E2 substantially equals E1 at the end or"the initial range, variation in time-overtheinitial range is produced byvariation inthe value;-of:E1,-.E1-,being:relatively low. for

In some practices s12 sinstantaneous ignitioniand' rising tosubstantially eequaleEz at. the El'ldsOf this initial time range.

lathe final. range aof relatively long-timeperiods,;-E2 is again: heldsubstantially constant at varelatively lowivalue (Ezminus mequalsj v.).and variations inztime. are again produced by variationsin the valuein'Ei. At the startoithis 11finalrange,- E1 substantially equals "E2but; with increasing time values OVGI'ilJhB range, E1 31)]?0-9gressively rises' above --E2.

Figs; 17 shows graphically .the. relation between the char-ging'-voltages- E1.- and 1E2 over the-three ranges of'timeF-adjustment.

;'In--F -ig. 118 we indicate diagrammatically how a rheostat;arrangement a-may-be :employedqin a charging device to applypotentialsiaEl and-E2 -select-ivel-y for any desiredvalue over the:three :ranges of time. A: control member shown in? dotted, lines carriesa first brush or :wiper -l 86 that-is'connectedi toaa chargingcontactEcby-a .wire Island also carries a-second brush'orawiperlSiPthat; is connected by a wire I9B to ascha-rging contact E2. Movementof the control member S51with-referenceto a timescalelercausesgthe=-,wiperi 36 to: traverse arheostat-resistancergenerally designated+92:- and simultaneously causes the -wiper N38 to traverse a;second-rheostat resistance generally designated?! 93.

The rhecstat resistance r l 92:" for c.0ntro11ing;-po-.=.tential;-E1:.isdivided intoath-ree; ranges by: con- :nection with alow voltage-awire z 233 and ahigh voltagewire its; the rangescorresponding, to the previouslymentioned initial,- mid? andfinar -timeranges. The initial-time-rangeg is-defined iby a lowvoltage-connection-l95 and: a high voltage :connection' the' midrange isdefined by the high voltage connection 1'98 1* and a secondlow Voltageconnection; I 91'; and the final-time range =is:-defined:by the lowvoltage connection 191 and --t-hesecondihighvoltage-connection1 I98.lihus,

the potential E 1 rises progressively as the control member I85movesgto-the right until azmaximum -valuewis reachedaat connection 196whereupon potential -E1 drops progressively until contact lEi'lf'iSreached and finally 'thepotentialrrisesto the maximum' again atconnection.- I 98.

"The" rheostatresistance 193. comprises a -con- ,tactzZddextending overthe initial timerange -a resistance 2ll extending over the midrange, andarsecond contact 292 extending over @the final time range. The contact290, the resistance 'zfll, and the contact 2:02. are in series; thecontact 280 :being'connecte'd to the high-voltageiwire i 94' andthe'contact' 2.52 being-connectedto the low. voltage wire:203. By virtueof thisarrangement; the "potential E2 varies'in the desired-manner asthecontrol member i85ismoved around the" time ,scale .lfil, the potential"E2 being-constant atva relatively; high voltage in the initial-timerange, progressively decreasing in the: midrange and again'rernainingconstant in thefinal range. It will .be noted that the describedarrangement causes E1 to equal E2 in the midrangarbothvalues increasingor decreasing asynchronously with movement, of the control member gl 85.

The manner in which such a "charging :device :isemployed may be readilyunderstood. The :op- .erator merely adjusts the-operating member I85 forwhatever period oftime'delayindetonation is :desired, the operator beingguided by referenceto the time scale 19!.

.Instead of employing a--m-idrange; between the two extreme ranges oftime as described. above, We may in some practices of our invention omitthe mi-drangesand provide; ion:directmorrelatio n 13 by arranging forthe values E2 and E1 at the end of the initial range to equal the valuesof E2 and E1 at the beginning of the final range. The relationship maybe understood by referring to Fig. 19. Note that E1 progressively risestowards the relatively high value of E2 over the initial range and thatin the final time range E1 is substantially constant while E2progressively decreases in value.

In Fig. we indicate diagrammatically how a rheostat arrangement may beincorporated in a charging device to supply potentials E1 and E2 overtwo time ranges correlated in the manner suggested by Fig. 19.

A control member 205 shown in dotted lines carries a first brush or.wiper 206 that. is connected to a charging contact E1 by a wire 201. Thecontrol member also carries a second brush or wiper 203 that isconnected by a wire 210 to a charging contact E2. For cooperation withthe contact 206 we show a rheostat means comprising a resistance 2| land an elongated contact 2 I2 in series, the outer end of the resistance2| I being connected to a low voltage lead 2l3 and the elongated contactbeing connected to a high voltage lead 2I5. For cooperation with thecontact 208 we show a second rheostat means com-, prising an elongatedcontact 2 I 6 and a resistance 2i! in series, the elongated contact 2H6being connected to the high voltage lead 215 and the outer end of theresistance 2|! being connected to the low voltage lead 2l3. It may bereadily understood that movement of the control member 205 to adjustcharges E1 and E2 for various time intervals will cause the voltages E1and E2 to vary in value in accord with Fig. 19.

The specific embodiments of our invention set forth above for thepurpose of disclosure will suggest to those skilled in the art variouschanges and substitutes under our basic concepts; we reserve the rightto all such departures that lie within the scope of our appended claims.

We claim:

1. In an electric ignition device for delayed detonation of an explosiveprojectile after the projectile is released from a holding means, thecombination of: condenser means in the projectile to hold an electriccharge, an igniter in the projectile; charging means for electricalcommunication with said condenser means while said projectile remains onsaid holding means; means to apply the charge of the condenser means tosaid igniter with time delay after the projectile is released from saidholding means; a normally closed safety shunt across said igniter toprevent flow of electric current therethrough; an electric conductorincluded in said shunt, said conductor being attached to saidprojectile; and means on the holding means engaging said conductor tosever the conductor and thereby open the shunt when said projectilemoves away from said holding means.

2. In a delayed ignition device for a unit, which unit comprises anexplosive projectile, holding means therefor, and a propelling charge,the combination of: a condenser circuit in the projectile; chargingmeans for contact with said unit to establish a given potentialdistribution in said circuit prior to explosion of said propellingcharge; means to progressively change the potential distribution in saidcondenser circuit over a period of time after the projectile ispropelled from said holding means; an igniter responsive to thepotential in said system at a predetermined point in said progressivechange in distribution; and a shunt including a Wire across said igniterto prevent energization thereof, at least a portion of said wire beingpositioned outside of said projectile and int he area occupied by 'saidpropelling charge whereby the explosion of said propelling charge willdestroy at least a portion of said wire and open said shunt.

3. In an electric ignition device for delayed detonation of an explosiveprojectile after the projectile is released from a holding means, thecombination of condenser means in the projectile to hold an electriccharge, an igniter in the projectile; charging means for electricalcommunication with said condenser means while said projectile remains onsaid holding means; means to apply the charge of the condenser means tosaid igniter with time delay after the projectile is released from saidholding means; a normally closed safety shunt across said igniter toprevent flow of electric current therethrough; an electric conductorincluded in said shunt, said conductor being attached to said projectileand extending into the holdling means; and means associated with theholding means and including an explosive charge in the holding means forsevering said conductor whenever the projectile is fired from theholding means by exploding said explosive charge.

JEROME J. KURLAND. JOSEPH J. KURLAND.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,623,475 Hammond Apr. 5, 19271,791,606 Ruhlemann Feb. 10, 1931 1,795,972 Ruhlemann Mar. 10, 19311,807,708 Ruhlemann June 2, 1931 1,907,279 Blomberg May 2, 19331,917,813 Ruhlemann July 11, 1933 1,917,814 Ruhlemann July 11, 1933FOREIGN PATENTS Number Country Date 530,348 Germany July 28, 1931581,491 Germany July 28, 1933 582,582 Germany 1933 91,592 Sweden Feb.24, 1938 864.373 France 1941

